Restraining mechanisms such as slide bolts and spring-loaded bolts are used in a variety of applications to restrain movement or lock components together. In one such application, the U.S. Navy uses a spring-loaded bolt to restrain a mine hunting device on a helicopter. The bolt is operated by means of a pull handle coupled to the bolt through a cable that is passed over a pulley. To disengage the bolt from its engagement hole or sleeve against a spring force, the handle is pulled with the cable being tensioned through the pulley to counter the spring force. The bolt can be locked in its disengaged position by locking the handle in place. There are several disadvantages to this arrangement.
A first disadvantage is that force can only be applied in one direction so the bolt cannot be forcibly urged into its engaged position. Rather, the bolt can only be returned to its engaged position by means of the spring force. However, problems such as slight misalignment between the bolt and its engaging hole, or sleeve or frictional loads experienced during the movement of the bolt, can prevent the bolt from moving into its engaged position. In response to such a situation, an operator tends to jiggle or push on the pull handle. Since this does not overcome any of the misalignment or frictional load forces, this does nothing to urge the bolt into its engaged position. Furthermore, jiggling or pushing the pull handle generally causes slack in the cable which can cause the cable to disengage from the pulley. Still another disadvantage is that the pull handle and cable offer no mechanical advantage when trying to overcome the spring force to withdraw the bolt. That is, a pull on the handle is transferred directly along the cable which is coupled in-line with the bolt. Thus, one must actually pull with a force greater than the spring force plus any other frictional forces. In addition, for applications requiring a large pull force, the locking of the pull handle after the bolt has been disengaged can be a struggle.